On Wed, 2017-05-03 at 08:52 -0700, Dan Williams wrote: > On Wed, May 3, 2017 at 8:31 AM, Toshi Kani <[email protected]> > wrote: > > This is a RFC patch for seeking suggestions. It adds support of > > badblocks check in Device DAX by using region-level badblocks list. > > This patch is only briefly tested. > > > > device_dax is a well-isolated self-contained module as it calls > > alloc_dax() with dev_dax, which is private to device_dax. For > > checking badblocks, it needs to call dax_pmem to check with > > region-level badblocks. > > > > This patch attempts to keep device_dax self-contained. It adds > > check_error() to dax_operations, and dax_check_error() as a stub > > with *dev_dax and *dev pointers to convey it to dax_pmem. I am > > wondering if this is the right direction, or we should change the > > modularity to let dax_pmem call alloc_dax() with its dax_pmem (or > > I completely missed something). > > The problem is that device-dax guarantees a given fault granularity. > To make that guarantee we can't fallback from 1G or 2M mappings due > to an error. We also can't reasonably go the other way and fail > mappings that contain a badblock because that would change the blast > radius of a media error to the fault size.
Does it mean we expect users to have CPUs with MCE recovery for Device DAX? Can we add an attributes like allow error-check & fall-back? Thanks, -Toshi
